This project deals with the phenomenon of natural killing (NK) in humans. We are investigating the effects of various biological response modifiers such as interferon on NK activity. In vivo, we are studying the effect of alpha interferon on NK cells of cancer patients. We will examine in detail the reasons for the transient suppression of NK activity 12 hours after interferon injection. In vitro, we will study the mechanism(s) involved in the loss of sensitivity of NK cells to suppression by prostaglandins after activation by interferon. Using monoclonal antibodies that react specifically with NK cells and have been shown to inhibit killing, we will attempt to better understand the interaction between NK cells and targets at the biochemical and molecular levels. Experiments will also be conducted to characterize NK-like cells obtained by various stimuli phenotypically, histochemically and functionally.